I've a chopper that can fly to good ranges (10~30m) and i am purchasing a video camera to install in it

Camera /transmitter spec. -
Button camera with audio +  1.2 ghz 500mw video transmitter (8x5x2) 130 g (my chopper can take this much weight with some modifications ).

Is it legal to use that AV Transmitter (1.2-1.3 frequency range 500mw power 3channels)

I'm buying it online from china , Is it possible to get this locally ? (this will cut off shipping)

any other thing that i must know before doing so?

http://www.quadkopters.com/product/fpv-kit-5-8g-200mw-av-txrx-system-with-sony-ccd-420tvl-camera/

You can ask him when it will be in stock.

Make sure the frequency of the radio isn't same as the frequency of the video transmitter.